Floods and Flash Floods: The Facts

Floods are among the most frequent natural hazards in New Jersey, and among the most devastating in terms of human hardship and economic loss.

The greatest risks occur in known flood plains when there is:

  • Intense rainfall over a short period of time,
  • Prolonged rain over several days, and/or
  • Ice or debris jams causing river or streams to overflow. 

Risks can occur anytime of the year.

  • Melting snow can combine with rain in the winter and early spring 
  • Severe thunderstorms can bring heavy rain in the spring and summer 
  • Hurricane or tropical storms can bring intense rainfall in the summer and fall. 

Floods and Flash Floods each provide unique risks.

  • Floods develop over several hours or several days. Streets can become swift-moving rivers, creating great danger for pedestrians and drivers. Basements, buildings and entire swaths of land can become inundated, leading to deadly hazards, dangerous structural damage, and lost property or crops.
  • Flash Floods occur with little or no warning and are deadly and fast moving. They can begin within the first hours of a rain event, or after a dam or levee failure, or following the sudden release of water held back by an ice or debris jam. Their power can roll boulders, tear out trees, destroy buildings and bridges, scour out new channels and can also trigger catastrophic mudslides.